The present invention concerns a timepiece including a GPS receiver, arranged for indicating the direction of a "target" destination or location from a "source" location where the GPS receiver is situated.
Timepieces able to indicate a particular direction are already known. By way of example, European Patent Application No. 95120717.4 can be mentioned, which discloses a timepiece arranged for indicating the direction of Mecca. This Application discloses an analog timepiece which incorporates a compass used to provide a reference axis (which is supplied by the direction of magnetic north).
One problem encountered in a timepiece including a compass lies in the fact that the permanent magnet associated with the compass is disturbed by the magnetic environment of the timepiece assembly. This problem becomes particularly inconvenient when the clockwork movement includes magnetic masses. One incomplete solution to this problem consists in moving the permanent magnet away from the magnetic masses, i.e. increasing the space requirement of the timepiece, which is contrary to the constant preoccupation of watchmakers. Moreover, such timepieces do not provide a simple solution for determining the direction of a "target" location. Such determination must take account of complex physical data such as the deviation between magnetic north and geographical north.
One difficulty for timepiece manufacturers consists in achieving an arrangement for such a timepiece which allows the desired direction to be provided, whilst attending to the usual constraints within the horological industry, such as space requirement.
A conventional solution to the aforementioned difficulty consists in incorporating, within an analog timepiece, a so-called GPS receiver. It will briefly be recalled that the abbreviation GPS designates a device connected to the Global Positioning System, which typically picks up coordinates and time data from a satellite. By way of example, this receiver needs to pick up signals transmitted by four different satellites to determine a location in a three dimensional space (latitude, longitude, altitude). The structure and operation of such a receiver are widely described in the state of the art, in particular in "Radionavigation Systems" by Borge Forssell.
By way of example, International Patent Application No. WO 96/21139 may be cited. This Patent Document mentions the fact that a GPS receiver can be used in a an analog timepiece, without a compass also being used therein. With reference to FIG. 2 of said International Patent Application, the hands of said timepiece indicate an angle W, which allows the timepiece user to move in the direction of a target direction Pn.
However, the Applicant of the present invention has noted that a GPS receiver arranged in an analog timepiece, does not, in itself, allow the direction of the target direction which the timepiece user wishes to know to be provided. Indeed, the Applicant of the present invention observes that said GPS receiver allows said user's spatial position coordinates to be provided, i.e. the direction of the target location in the referential formed by the four satellites, the coordinates of the target location having been previously stored in said GPS receiver. In other words, said user needs to use a reference axis, with respect to which the direction of the location can effectively be defined.